Vulnerability of Water Resources and Trophic State of the Santa Lucía river
lower basin and estuary to Climate Variability and Change.
Caffera MR1,2, M Bidegain1,3, F Blixen1,3, CH López1, JJ Lagomarsino1, GJ Nagy1 and K Sans1.
1: Project AIACC LA-32- Facultad de Ciencias, UdelaR; 2: Consultant of Unit of Climate Change,
Directorate of the Environment; 3: Directorate of Meteorology, Ministery of Defense.
This paper describes findings on the vulnerability of water resources of the Santa Lucía
river basin (SLRB, 13,681 km2, Southern Uruguay) to Climate Variability and Change.
SRLB sustain intensive agricultural, host 20,000 hs of wetlands rich in biodiversity and
supplies drinking water for 60% of the nation’s population. Continental aquatic systems
like SLRB are links between atmosphere, pedosphere, biosphere and coastal ocean. We
are in need to understand dynamic responses of these systems which are worlwide
showing a suit of syndromes of global change (e.g. river flow changes and
eutrophication) and their response to projected scenarios. Lack of information and
knowledge about some relevant processes difficults to build vulnerability scenarios.
That is why we focus on building scientific capacity to understand basic processes and
facts. Some findings for the last 3 to 5 decades are: SLRB is subject to increasing
agricultural intensification, temperature rise (1º C), 20% increase in average
precipitations and seasonal changes, sea level rise (10 cm), increased ENSO-related
variability. Most rates show acceleration since early 80s: Droughts, floods and storm
surges are affecting settlements, soil erosion, runoff, ecosystems and trophic state.
Trophic state is highly sensitive to an increase in agriculture intensification.
precipitations, runoff and soil erosion. Monthly river heights are consistent with both
cold and warm phases of ENSO during spring time (O-N-D). This is a new finding,
since previous research in Uruguay found significant link with ENSO phases only in
northern basins, and especially good agreement during La Niña events. An increase in
magnitude of major discharge events is observed in the last 25 years, by means of daily
height series. This fact is consistent with the precipitation trends and implies an issue for
land use and human settlements. We analyzed the vapòr flux regime in lowers levels of
the atmposphere, while occurring heavy showers conducting into floods. Primary
results suggest that water vapor flux could be eventually advected from the near ocean
region, more commonly than in Northern watersheds. During summer time (D-F) and
La Niña events, decrease in precipitation and increase in temperature and evaporation,
impact agriculture and drinking water supply. Accelerated rates of change suggest that
these sectors will be heavily impacted in the near future. Losses of coastal land and
biodiversity (e.g. estuarine wetlands and birds), damage to infrastructure and blocking
of the runoff resulting from sea-level rise could occur in low-lying areas and could
increase the risks of floods.